US2605118A - Individual wheel suspension, including caster and camber adjusting means - Google Patents

Description

J. H. BOOTH ET AL INDIVIDUAL WHEEL SUSPENSION, INCLUDING July 29, 1952 CASTER AND CAMBER ADJUSTING MEANS 4 Sheets-Sheet 1 Filed Nov. 22, 1947 MN NR 6v MN R QN H Q n m E H V M \N M July 29, 1952 J. H. BOOTH ET AL 3 INDIVIDUAL WHEEL SUSPENSION, INCLUDING CASTER AND CAMBER ADJUSTING MEANS Filed Nov. 22, 1947 4 Sheets-Sheet 2 -\l\ IIIIH L M 1 Q j Y Q 03* T a a a fi Q Q N N I Lg] O l I H Q I M I M W O W EVEHTIFE/ 2& 2275.

July 29, 1952 J. H. BOOTH E L 2,605,118

INDIVIDUAL WHEEL SUSPENSI INCLUD G CASTER AND CAMBER ADJUSTING MEAN Filed Nov. 22, 1947 4 Sheets-Sheet 5 36 F 4 I .J

In rimwg 43 H. BOOTH J. VIDUAL ASTER AN CLUDING ET A W EL SUSPENSION AMBER ADJUSTING MEANS INDI July 29, 1952 4 Sheets-Sheet 4 Filed Nov. 22, 1947 .v H 2 7 EH0 v am,

Patented July 29, 1952 ING CASTER MEANS AND CAMBER ADJUSTING James H. Booth, Corunna, and Bernard E. Ricks, Ferndale,'fMich., assignors to Thompson Products,':;In,c.,' Cleveland, Ohio, a corporation of ApplicationNovemb'er 22, 1947, Serial No. 787,518

' r-claims- .(Cl. 2s0-es.2)

This invention relates to wheel suspension apparatus for automobiles. More particularly, this invention relates to wheel suspension apparatus for automotive vehicles wherein the swivel joints securedat the outer ends of the lower and upper control arms arecapableof adjustment to regulate the camberand caster-angles of the vehicle.

As is well known in tl1e-automotive field,the

front steering road wheelsof-a'n' automobile are inclined downwardly and inwardly at an angle from the vertical. This angle is known as the camber angle. In addition the vertical steering axis is also tilted toward the rear to give the wheels a trailing effect for causing the automobile to steer a straight course. as the caster angle.

When the Wheel suspension system is originally assembled, the mechanism is installed at the correct camber and caster angles. However, due to wear, collisions or running intocurbin g or the like, the wheel suspension system is often jarred out of alignment. v V

In accordance with the teaching of the present invention adjustments ior'cambe'r and caster are quickly and easily made by adjusting joints located at the outer ends of the upper and lower control arms of a typical independent wheel suspension system. Thesejoints arepreferably of the ball joint type and are connected to the upper and lowerends of a rigid steeringknuckle which carries the wheel spindle. Q Axial adjustment of a stem on the upper ball joint housing causes pivoting of the spindle in a substantially vertical plane through the axis of the spindle about the lower ball joint andthus affords a means for adjustingthecamber angle. Rotation of a screw member having one threaded member eccentrically disposed around the stem of the lower ball joint housing shifts the steering knuckle laterally or forwardly and rearwardly relative to the upper ball joint; This'shiiting adjusts the caster angle. 1 H

This angle is known There is further provided ,inthishinvention I means for locking eachadjustment mechanism in place after the camber. andcaster. adjustments have been made. In one embodiment this locking means is provided by a split clamping" sleeve rigidly secured to the control arm and arranged to be pressed into. clamping engagement about the screw member of the adjustment mechanism-,while in a second embodiment a lock nut is disposed over a split clamping sleeve which has a tapered exterior threaded surface 'and is arranged to be pressed tightly against the stem of the ball joint to lock the assembly. L

Thus, adjustments for camber and caster can quickly be made by means of screw members which may be conveniently manipulated by a simple end wrench.

It is therefore an object of this invention to provide apparatus for quickly and accurately adjusting the camber and caster angles of an independent wheel suspension.

Another object of this invention is to provide wheel suspension apparatus whereby adjustments for camber and caster may bemade independently of each other. j A further. object of .this invention is to provide a wheel suspension having adjustable ball joints connecting tthe'steering knuckle and the wheel arms arranged to shift the'axis of the steering knuckle to selectively vary the camber and caster angle of the wheel.

It'is a specific object of this invention to provide a wheel suspension, system, employing ball type joints, saidjoints having screw connections for shifting the axis of the steering knuckle to adjust the camber and caster angles for the wheel.

Other and further objects of this invention will be apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings, which illustrate one embodi: ment of the invention.

Onthe drawings: V Figure 1 is afragmentar'y rear end elevational view with parts in vertical cross section and with other parts broken away, of an adjustable dirigible wheel suspension apparatusof this invention; Figure 2 is a fragmentary top'plan view of the adjustable wheel suspension apparatus of this invention; V.

Figure 3 is a,jver tical sectional view, with parts in elevation, taken on line III-III of Fig: 2; i g

Figure tis a fragmentary vertical sectional view taken substantially on line IVIV ofFig. 3;; Figure .5..is a' fragmentary verticalsectional view taken.on.line.VV of Fig. 1; j I j Figure 6' is a fragmentaryrvertical sectional view taken on line VI-.VI'of Fig. 5 g. v j Figure '7 is a diagrammatic sketch showing the camber adjustments according to the teaching of this invention; i w,

Figure 8 is a diagrammatic sketch of a portion of the adjustment mechanism of the .wheelsus: pension device of the present invention, showing particularly'the' eccentricity of .thexmembe'rsrof this adjustment device; I

- Figure 9 is a diagrammatic Sim-tag when.

with parts in vertical cross-section and with other In Fig. 1 a typical right front wheel suspension,

arrangement for an automobile is shown, as

viewed from the rear of the car. It will, of course, be recognized that the complete system includes an identical suspension device, oppositely disposed at the left side of the vehicle. The novel adjustable ball joints of the present invention must be mounted on the wheel suspension at both sides of the vehicle, since the camber and caster angles of each steering wheel must be adjusted.

Reference numeral designates the brake drum of a typical road wheel rotatably mounted in the conventional manner on a wheel spindle l i. The spindle l l is preferably formed integral with a steering knuckle I2, which is supported for swinging, steering movement at its upper and lower ends in ball joints It and 35, respectively. Steering movement of the steering knuckle i2 is accomplished through a rearwardly extending steering arm [3 which is controlled from the drivers seat through the conventional tie-rod and drag link.

.The upper ball joint [4 is arranged to permit swinging of the knuckle l2 and at the same time is adapted to accommodate pivoting in a substantially vertical plane of an upper control arm 5.. The control arm It, as seen in Fig. 2, comprises a U-shaped member having leg portions Mia and 16b straddling a shock absorber !8, being pivotally attached to opposite ends of the operating shaft IQ of the shock absorber. A plurality of bolts 20 secure the shock absorber to a cross frame member 2| of the vehicle.

As best seen in Figs. 1, 2 and 3, the cross part or bight [6c of the U-shaped control arm It has an aperture therethrough at its central portion receiving an adjusting assembly 24. The housing of the adjusting assembly 24 is welded or otherwise affixed to the arm l6 and will be described in detail hereinafter. A threaded stem 25 integral with the housing of the ball joint It extends outwardly therefrom intothe housing of the assembly 24. A ball stud 26, disposed for pivoting and rotation in the joint M, has a tapered shank portion wedged in a hole in the top of the knuckle [2 by means of a nut threaded on the end of the stud. The lower ball joint I is arranged to accommodate the swinging, steering movement of a stud Z'Iwhich has a tapered portion wedged in a hole in the bottom of the knuckle I2 by a nut threaded on the end of the stud. The joint 15 also permits pivoting in a substantially vertical plane of a lower control arm 29 which straddles, at itsinner end, a downwardly extending. portion Zia of the frame member 2|, being connected at either end of the portion'2 la to a pivot pin 30 extending therethrough. Upper pivoting movement of the control arm 29 is resisted by a coil spring 32 which has its lower end disposed in an annular groove 29a of a support plate aflixed to the lower control arm 29, and its upper end guided about adownwardly projecting cylindrical portion 21b of the frame member ..2I.

As seen in Fig. 1, the bight portion or cross member 2% at the outer end of the lower control 23 supports a screw type adjustment asy. 33, which includes a threaded stem 35,

4 Fig. 5, formed integral with the housing of the ball joint l5.

Thus, it is seen that the road wheel is mounted on the upper and lower control arms by means of .upper and-lower ball joints which accommodate pivotal swinging movements of the arms as well as steering movements of the knuckle i2. It is also evident that if the effective length of the upper control arm IE is shortened or lengthened, the steering knuckle l2, and consequently the wheel, will pivot about the lower ball joint [5 inclining the upper part of the wheel inwardly or outwardly with respect to the vertical. In the present invention this adjustment to the effective length of the upper control arm I6 is made through the screw assembly 24, thus providing means for regulating the camber angle.

Also, it will be readily seen that if the stem 35 of the lower ball joint I5 is displaced toward the front of the vehicle or toward the rear of the vehicle, the axis of the steering knuckle l2 which determines the steering axis of the wheel, will pivot forwardly or backwardly about the upper ball joint [4. This pivoting of the steering axis wheel about the upper ball joint is effective to make adjustments to the caster angle and is carried out in this invention by means of the assembly 33 and the adjustable screwmembers that are eccentrically mounted therein.

Camber adjustments In Figs. 3 and 4, the adjusting assembly 23 is ilustrated in detail. It comprises the threaded adapter arm 25 of the joint it which has a smooth shank portion 25a and a left-hand threaded portion 25b of smaller diameter than the shank portion 25a. A bushing 36, surrounds the arm 25 having threads on its inner diameter for a portion of its length, said threads mating with the threads of the arm 25. At one end a nut 36a is integrally secured to the bushing 36. A clamping sleeve 38, having an internal righthand threaded portion extending for a portion of its length and a smooth bore portion for the rest of the length, is split at one side, Fig. 4,

and has a pair of projecting flanges 38cfor receiving an adjusting bolt 39.

The bushing 36 has a diagonal slot 36b-cut through its wall so that, as the bolt 39 is tightened, a clamping action will take place through both the outer and the inner threads of the bushing causing it to tighten securely on the threads of the adapter arms 25. The clamping sleeve 38 also looks the bushing tightly against the smooth shank 25a of the arm 25 and hence any impact on the wheel will be taken through the smooth shank portion of the arm 25 and not through the threads.

Rotation of the ball joint I4 with respect to the clamp 38 is prevented by a projecting member 38d which extends into a slot 250 of the joint housing (Fig. 3).

As. previously mentioned the bight portion member lficof the upper control arm i3 receives and is secured as by welding to the clamping sleeve 38 of the adjustable member24. Therefore the clamping sleeve 38 is heldagai'nst rotation' by the member I and the ball jointlt is held against rotation by the projection 38d Then, with the bolt 39 of the clamp. 38 loosened, the eiTectiVe length of the upper, control arm can be varied by turningthe nut 36a of the bushing 36 in a clockwise direction. This will cause the bushing 36 to move into the threaded portion of the clamping sleeve 38.on the right-hand passes through the center of the tire on the wheel.

Thus, there is no camber angle in this illustration. The line 13 indicates how the wheel can be pivoted to the right about the lower ball joint I by increasing the effective length of the upper control arm I5, thus providing a positive camber angle. The line C illustrates how counterclockwise rotation of the nut a, shortens the effective length of the control arm [6 and causes the wheel to pivot in the opposite direction to provide negative camber.

Thus, there is provided in this invention a simple, eiilcient screw-type adjustment member by means of which the camber angle of the steering wheel can be quickly and accurately adjusted.

Caster adjustments The adjustment assembly 33 on the lower control arm is illustrated in Figs. 5 and 6. It is essentially the same as the adjustment assembly 2 havinga right-hand threaded stem member 35 screwed into a longitudinally split bushing 15 which has a bolt head portion 46a and righthand'external threads in contact with the threads of a split clamping sleeve 42. A bolt 43 is used to securely lock the clamping sleeve 42 around the bushing and the arm 35. As in the adjusting assembly 24, the arm 35 has a smooth shank portion 35a in contact with a smooth portion of the bore of the bushing 53, so that impact loads may be transmitted through the shank rather than through the threads.

It is to be noted, however, that since the bushing of this adjustment assembly 33 has righthand threads on its external and internal surfaces, rotation of the nut 45a will not cause lengthening or shortening of "the control arm since the movement of the bushing in relation to the clamp member will be counteracted by the movement of the bushing in relation to the threaded arm members 35.

Adjusting assembly 33 difiers from adjusting assembly 24 in that the stem 35 is eccentrically disposed in the bushing 40 as shown in Fig. 6. In Fig. 8 the letter D indicates the distance between the center S of the stem 35 and the center T of the bushing 40. It will be readily seen that if the clamp sleeve 42 is loosened and the bushing 40 is rotated through 180, the center 3- of the stem will move to position S and be displaced a distance equal to twice the distance A between the original centers. of the center B of the stem 35 will be best understood by referring to Fig. 6 wherein it is clearly shown that the bushing 40 rotates in the clamp 42 and the stem 35 moves with the bushing.

In Fig. 9, the points X and Y indicate the maximum adjustments of the stem 35 about the upper ball joint M which is indicated by the letter Z. Y

Thus there is provided in this invention a means for adjusting the caster angle by eccentric adjustments of the stem 35 in the bushing 40. It will of course be understood'that whil'e'Fig. 8

The displacement illustrates the maximum adjustment of the arm.

35, any adjustment between these points can be had by a corresponding rotation of the nut 55a.

In Fig. 1 it is seen that the adjusting nut 36a on the upper control arm and 55a on the lower control arm are easily reached from the front of the vehicle or from underneath the vehicle thus providing convenient access to the mechanism for adjusting the camber and caster angles.

A second embodiment of the wheel suspension apparatus of this invention is illustrated in Figures 10 and 11 wherein parts substantially identical with parts described in connectionrwith Figures 1 to 9 have been marked with the same referencenumerals. i

In Figure 10 the wheel spindle oil on the knuckle I2 is supported through ball joints M and [5 from the control arm I 5 and 29 as in the construction of Figures 1 and 2. However, in

Figure 10 somewhat different adjusting assem-,

blies between the control arms and ball joints are provided. Thus an upper adjusting assembly 5-5 mounted in the bight of the upper control arm [6 increases or decreases the effective length of this control arm by shifting a stem 450i the ball joint [4 whenever a bushing ll of the assembly is rotated. The stem "55 has a smooth shank portion 5611, a left-hand threaded portion 1Gb of smaller diameter than the shank portion 46a and an intermediate smooth stem portion 450 of smaller diameter than the threaded portion 45b. The bushing 57 surrounds the threaded portion 46b and has internal threads that mate with threads of the stem portion 55b.

The bushing t! has a hexagonal head portion Ma and an external, right-hand threaded portion 411) which is arranged to be threaded into .a tapped hole Hid in the bight or cross piece liig of .the U-shaped arm It. A split sleeve portion |6e of the bight Hig extends outwardly therefrom to receive in its bore the smooth shank 45a of the stem 46.

The sleeve Hie has a tapered threaded external surface Which receives a locking nut 49. 7

As best seen in. Figure 11, the split sleevelfie has a slot 55 Which extends along the entire length of the sleeve providing a clamping means movable against the stem 45 of the ball joint is by the locking action of' the nut 55. An up- Wardly projecting lug 51, on the stem 55, extends into the. slot 55 to prevent rotation of the ball joint M in the sleeve Hie.

When the clamping action of the sleeve lee on the stem 46 is released by backing the locking. nut 49 off the tapered portion of the sleeve, the effective length of the upper control arm can be varied by threading the bushing 47 in or out of In the embodiment illustrated in Figure 10, caster adjustments are made by means of an ad-' justing assembly 52. This assembly comprises a stem 54 of the ball joint 15 which has a smooth shank portion 54a, a right-hand threaded por-' tion 54b and an intermediate portion E le-of re-,

dueeddiameter. A bushing 55, which has a diagonal slot 551a cut through its wall, surrounds pivoted outwardly on.

the; stem 54 having a smooth bore portion disposed snugly over the shank 54a and; a portion 55b threaded over the portion-54b of the stem.

The inner end of the bushing 55i includes. a hexagonal head 55c and a right-handi threaded. portion 55d which extends for a. portion of the: length of the bushing and is threaded: into a tapped. hole 290 in the bight 29g. of the lower control arm 29. A. sleeve 29d is formed; integral with the bight member 299 and extends outwardly therefrom to receive in its-bore the smooth-outer surface of the bushing 55 The sleeve ZQrZJ-has a.

A pair of resilient bumper members 53 and 59. aresecured to the outer end oftheframeZl-i and. are arranged to contact'bumper plates 60 and- B t secured, as by riveting to the bightor cross part" ofthe upper andlowercontrol. arms respectively.

Itwill, of course, be understood that various details-of construction may be varied through a wide range without departingfrom'the.principles of this inventionand .it is, therefore, notlthe purpose to limit-the patent granted hereon otherwisethan necessitated by the scope of the appended claims.

We claim as our invention:

1'. In a control arm type wheelsuspensionincluding a ball joint on the. end of the control arm, said ball joint having a housing: with a stem extending therefrom, said stem. having a smooth shank portion adjacent the housing and a threaded portion remote. from thehousing, a bushing having an external threadedportion; an internal threaded portion in threaded engagement-with the threaded portion of said: stem and a smooth portion surrounding the smooth shank portion of the stem, aclamp memberronsthe-comtrol'arm and'havingan internal threaded portion. in threaded engagement with the external: thread 1 of the bushing together with aniinterna'llsmooth portion overlying-the smoothportion'of thebushing,.the internal threads of said; clamp member being of the opposite hand than the internal threads of the bushing, and means for contracting the smooth portion-of the clamping-member about'the smoothportions' ofthe bushing and stem to lock the; assembly against relativerota' tion whereby-th effective length. of." the. control-l arm is adjustably varied by loosening of the clamp and by rotation of the bushing.

2. An adjustable wheel suspension comprising upper: and lower control arms, a-steering knuckle carried'by said control arms, an upper ball-type. joint connecting said steering knuckle with said upper control arm, a lower ball type-joint-connecting said steering knuckle: with said lower control arm and means for adjusting; the effective length of? one: of said control armsto'pivot.

the steering. knuckle about the ball type jjoint connected tothe other? control arm,. saidmeanscomprising'an adapter" arm secured tothe house ing, of theball joint connected to said one com-- trol' arm, a. bushing coaxially. threaded: on said.

adapter arm, a. clampsecuredito' said one control arm and threaded on. said". bushing, the. threads:

between the bushing'and: the adapter arm. being of opposite hand to. the threads between... the. bushing and the clamp, whereby rotationof said bushing. in. one direction causes said bushing to move into said clamp and: causes. said. adapter. arm to-.move out of said bushing to. thereby: iiicrease-the effectivelength'of the said. one control arm,.and.-whereby. rotationmf said bushin in the.

opposite direction: causes said bushing to back out. ofsaidi clamp and causes said adapter arm to move:into said bushing. to. decrease the effec' tive: length. of thesaid. one-control arm.

3. In a wheel suspension. system includinga controlarm, a ball jointatithe'endof said'control arm; said joint comprisinga h'ousing member and a ballmember, a caster. adjustingdevice comprising an adapter arm securedito one'of. the-members of the ball joint andiprov-ided withthreads;

a bushing threaded in the control arm and.

threaded on the said adapter arm, the threads-betweenthebushing. and the-adapter arm being of the same hand and" of the same pitch. asi'the' threadsbetween the, bushing and. said control arm, the axis of said adapter arm being eccentrically disposed relative to the axis of said bushing, whereby said adapter. arm. is displaced transversely of itsaxiswhensaidbushing is rotated,

theeffective length of the control armremaihing.

constant, and means. for retaining thedevice in the adjusted position;

4. In a. wheel suspension. system including. a

controlarm, a ball jointatfthe endofsaidflcont'rol'.

arm, acaster adjusting device comprising an adapter arm secured tothe housing ofthe ball joint, and having a smooth shank portion adjacent the joint, the. remainder of the adapter armbeing threaded, a split bushing having a threaded bore with threads that mate with the threads ofthe adapterv arm and a smooth portion for contact with the-shank of. saidiadapter arm, said bushing being provided on its external surface with auportionithreadedinr thesame direction, and with the same pitch. as the internal. threads in saidbore. andwith a smooth. external shank portion, a cla mp member secured. to. the control arm and-having internal. threads mating with the external threadson said-bushing. and a.

contractible: smooth portion surroundin the smooth shank portion of. the bushing, and a. clampingmeans associated with the. clamp memher for contracting. the. smooth portion of the.

clamp member on the smooth. portion of the.

bushing for locking the thread surfaces of the clampmember with-the bushing-and the threaded bore ofthe'bushing with the adapter arm, the bore of saidbushing being eccentrically disposed with'relation to theexterior. surface of the bush.- ing, whereby the, adapter arm disposed. in said bushing will, be shifted: transversely of its axis.

upon rotation of-said bushingandsimultaneously held stationary withirespect to itsaxial direction.

5,. In, a control arm typer wheel suspension including .a first control armand'a secondcontrol arm, av steering knuckle, afirstball. joint univer sally connecting the. steering, knuckle with the first control arm, asecondball joint universallyconnectingsaid steering knuckle with said second control arm, first means associated with said first control arm for" adjusting the efiective length of; said. first control arm, said-first 'means. comprising a=first bushing! threaded. externally and: having, a' concentric. threaded bore, a: first.

adapter arm secured to the housing of said first ball joint and having a threaded portion, said first bushing being threaded in said first control arm and threaded on said first adapter arm, the threads between said first bushing and said first control arm being of opposite hand to the threads between said first bushing and said first adapter arm, second means for displacing in a fore and aft direction the end of the steering knuckle connected to the second'control arm, said second means comprising a second bushing having external and internal threads, a second adapter arm secured to the housing of said second ball joint and having a threaded portion, said second bushing being threaded in said second control arm and threaded on said second adapter arm, the axis of said second adapter arm being eccentric of the axis of said second bushing and the threads between the second bushing and the said second control arm being of the same hand and of the same pitch as the threads between the second bushing and the said second adapter arm whereby adjustment of caster may be made by rotation of said second bushing without affecting the camber adjustment and adjustment of the camber may be effected by rotation of said first bushing without affecting the caster adjustment.

6. An adjustable wheel suspension comprising upper and lower control arms, a steering knuckle carried by said control arms, an upper ball type joint connecting said steering knuckle with said upper control arm, a lower ball type joint connecting said steering knuckle with said lower control arm, and means for adjusting the effective length of one of said control arms to pivot the steering knuckle about the ball type joint connected to the other control arm, said means comprising an adapter arm secured to the housing of the ball joint connected to said one control arm, a bushing coaxially threaded on said adapter arm, a clamp secured to said one control arm and threaded on said bushing, the threads between the bushing and the adapter arm being of opposite hand to the threads between the bushing and the clamp, whereby rotation of said bushing in one direction causes said bushing to move into said clamp and causes said adapter arm to move out of said bushing to thereby increase the effective length of the said one control arm, and whereby rotation of said bushing in the opposite direction causes said bushing to back out of said clamp and causes said adapter arm to move into said bushing to decrease the effective length of said one control arm, said clamp comprising a split sleeve portion having an external tapered threaded surface, a locking nut having an internal tapered threaded surface cooperating with said external tapered threaded surface of said sleeve portion whereby rotation of said locking nut contracts said split sleeve portion to clamp said adapter arm in adjusted position.

7. In a wheel suspension system including a control arm, a ball joint at the end of said control arm, a caster adjusting device comprising an adapter arm secured to the housing of the ball joint and provided with threads, a split bushing threaded in the control arm and threaded on the said adapter arm, the threads between the bushing and the adapter arm being of the same hand and of the same pitch as the threads between the bushing and the said control arm, the axis of said adapter arm being eccentrically disposed relative to the axis of said bushing whereby said arm is displaced transversely of its axis when said bushing is rotated and the eifective length or" the control arm remains constant, means for retaining the device in the adjusted position, said means comprising a split sleeve attached to said control arm and surrounding said bushing, said split sleeve having a tapered threaded external surface, and a locking nut having an internal threaded tapered surface cooperating with the external threaded surface of said sleeve whereby rotation of the locking nut contracts the split sleeve portion about said split bushing for clamping said adapter arm in adjusted position.

JAMES H. BOOTH. BERNARD E. RICKS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 19,482 Baker Mar. 5, 1935 373,381 Snyder Nov. 15, 1887 900,717 Feaster Oct. 13, 1908 923,724 Sprado June 1, 1909 2,099,114 Holmes Nov. 16, 1937 2,115,919 Slack May 3, 1938 2,123,087 Leighton July 5, 1938 2,154,569 Hicks Apr. 18, 1939 2,226,406 Krotz Dec. 24, 1940 2,238,879 Dauben Apr. 22, 1941 2,290,923 Wahlberg July 28, 1942 2,405,458 Slack et al Aug. 6, 1946 2,444,666 Orain July 6, 1948 2,544,331 Kogstrom Mar. 6, 1951 FOREIGN PATENTS Number Country Date 286,424 Great Britain Mar. 8, 1928 394,501 Germany May 1, 1924 OTHER REFERENCES Publication: Aeronautics of May 17,

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